xzcat: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/xzcat - from package: xz

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/xzcat - from package: xz-utils

You may install the required package with command apt-get install {package}

Error in other languages:
xzcat: bevel nie gevind nie
xzcat: comandă negăsită
xzcat: comando não encontrado
xzcat: commande introuvable
xzcat: command not found
xzcat: käsku ei ole
xzcat: không tìm thấy lệnh
xzcat: komanda nerasta
xzcat: Kommando nicht gefunden.
xzcat: kommandot finns inte
xzcat: komut yok
xzcat: nie znaleziono polecenia
xzcat: níor aimsíodh an t-ordú
xzcat: no se encontró la orden
xzcat: no s'ha trobat l'ordre
xzcat: opdracht niet gevonden
xzcat: parancs nem található
xzcat: perintah tidak ditemukan
xzcat: príkaz nenájdený
xzcat: příkaz nenalezen
xzcat: команда не найдена
xzcat: командата не е открита
xzcat: 命令找不到
xzcat: コマンドが見つかりません